Anion complexes of ferrous porphyrins

Mincey, Terry; Traylor, T. G.

doi:10.1021/ja00497a061

Cited by 92 publications

(51 citation statements)

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“…The strong H-bond is believed to result in increased electron density on the histidine imidazole-Fe-porphyrin system, which would aid in stabilizing both the heme and radical electron-deficient centers that exist in compound ES. Several studies have been published that agree with this idea (Mincey & Traylor 1979;Traylor & Popovitz-Biro, 1988;Fujita et al, 1983). Strong proximal H-bonding might therefore be expected to be a general feature of the heme peroxidases in general.…”

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confidence: 65%

Active Site Structure in Cytochrome c Peroxidase and Myoglobin Mutants: Effects of Altered Hydrogen Bonding to the Proximal Histidine

et al. 1996

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The globins and peroxidases, while performing completely different chemistry, share features of the iron heme active site: a protoporphyrin IX prosthetic group is linked to the protein by the proximal histidine residue. X-ray absorption spectroscopy provides a method to determine the local structure of iron heme active sites in proteins. Our previous studies using X-ray absorption spectroscopy revealed a significant difference in the Fe-N epsilon bond length between the peroxidases and the globins [for a review, see Powers, L. (1994) Molecular Electronics and Molecular Electronic Devices, Vol. 3, p 211 CRC Press Inc., Boca Raton, FL]. Globins typically have an Fe-N epsilon distance close to 2.1 A while the Fe-N epsilon distance in the peroxidases is closer to 1.9 A. We have proposed [Sinclair, R., Powers, L., Bumpus, J., Albo, A., & Brock, B. (1992) Biochemistry 31, 4892] that strong hydrogen bonding to the proximal histidine is responsible for the shorter bond length in the peroxidases. Here we use site-specific mutagenesis to eliminate the strong proximal hydrogen bonding in cytochrome c peroxidase and to introduce strong proximal hydrogen bonding in myoglobin. Consistent with our hypothesis, elimination of the Asp235-His175 hydrogen bond in CcP results in elongation of Fe-N epsilon from approximately 1.9 to approximately 2.1 A. Conversely, introduction of a similar strong proximal hydrogen bond in myoglobin shortens Fe-N epsilon from approximately 2.1 to approximately 1.9 A. These results correlate well with other biochemical data.

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confidence: 65%

Active Site Structure in Cytochrome c Peroxidase and Myoglobin Mutants: Effects of Altered Hydrogen Bonding to the Proximal Histidine

et al. 1996

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“…Teraoka et al [215] have shown that a characteristic of peroxidases is an Fe-N stretching frequency for the iron(II)-proximal histidine linkage that occurs 20 cm À1 higher than the corresponding vibrations of hemoglobin or myoglobin. The high m Fe(II)-his frequencies found for peroxidases are attributed to partial imidazolate character of the proximal histidine, induced by a hydrogen bond between the proximal histidine and an aspartate residue [202,[216][217][218][219][220][221], which are His-170 and Asp-247 for HRP-C. The m Fe(II)-his frequencies exhibit characteristic pH-dependence [222][223][224] that correspond to heme-linked ionizations of the ferrous enzyme [174,225].…”

Section: Discussionmentioning

confidence: 99%

Resonance Raman spectroscopy of oxoiron(IV) porphyrin π-cation radical and oxoiron(IV) hemes in peroxidase intermediates

Terner¹,

Palaniappan²,

Gold³

et al. 2006

Journal of Inorganic Biochemistry

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“…Large changes in wavelength would be expected if the iron-histidine bond were ruptured, since in model compound data it was reported that the Soret maximum shifts from -420 nm to -390 nm upon going from six to fivecoordination when the nitrogenous fifth ligand is lost (27). Similarly, when a weak field ligand, such as H20, occupies the fifth position in a CO-bound heme complex, the peak of the Soret transition is shifted substantially to shorter wavelengths as compared with complexes with imidazole at that position (28,29). We conclude that for CO-bound Mb at low pH, the heme is six-coordinate and the fifth ligand is histidine.…”

Section: Discussionmentioning

confidence: 99%

Metastable intermediates in myoglobin at low pH.

Han

Rousseau

Giacometti

et al. 1990

Proc. Natl. Acad. Sci. U.S.A.

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Resonance Raman and optical absorption spectra of ligand-free (deoxy) myoglobin and CO-bound myoglobin (MbCO) at pH 2.6 have been measured by using continuous-flow/rapid-mixing techniques. The spectra of deoxy myoglobin at low pH within 6 ms of the pH drop demonstrate that the iron-histidine bond has been ruptured but that the heme is still five-coordinate. Comparison with data from model complexes indicates that a weak-field ligand, such as a water molecule, is coordinated at the fifth position. The Raman spectrum of MbCO at low pH has an Fe-CO stretching mode that is characteristic of a six-coordinate heme with an unhindered Fe-CO moiety. Immediately following the pH drop in this case, there is no indication that the iron-proximal histidine bond is broken. Three different structural changes are detected at low pH: (i) the iron-proximal histidine (F8) bond in ligandfree myoglobin is broken and replaced by a weak-field ligand, (ih) the distal pocket in MbCO is opened, and (iii) protein constraints on the heme group in MbCO are relaxed. Previous conclusions that the kinetics of CO-binding in hemoproteins at low pH is modified by rupturing the iron-proximal histidine bond are supported by these new results which, however, demand a more complete reevaluation of the phenomenon.Since heme proteins carry out diverse biological functions, a great deal of effort has gone into determining the molecular basis for their properties. Myoglobin (Mb) is one of the simplest heme proteins and has been extensively studied in order to understand the factors that control the binding and release of oxygen, its physiological ligand, as well as CO, which is a convenient oxygen substitute for laboratory studies (1, 2). In several reports, the binding of CO to Mb (3,4) and other heme proteins (5, 6) has been monitored after a rapid drop in pH. For most Mbs and monomeric hemoglobins (Hbs) (3, 4) and for human tetrameric Hb (5), it was found that at low pH (-2.5) a large increase in the CO-binding rate occurs. This was interpreted as a consequence of protonation of the proximal histidine and the associated rupture of the iron-histidine bond, thereby allowing the iron atom to adopt an in-plane position and thus lower the barrier for CO binding. The rupture of the iron-histidine bond was supported by the absorption spectra, which, in the case of the ferrous ligand-free protein at low pH, are similar to those of fourcoordinate model compounds (4).Resonance Raman scattering is a well-suited technique to determine ligand coordination and the structure of the active site in heme proteins. Modes in the high-frequency region are known to be sensitive to axial coordination, porphyrin macrocycle core size, and heme doming (7). Axial ligand modes are often present in the resonance Raman spectrum and may be used to determine the heme coordination and the structure of the ligands (8,9). In addition, the properties of the iron-histidine bond may be monitored, since the ironhistidine stretching mode is present in five-coordinate ferrous hemes (1...

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Anion complexes of ferrous porphyrins

Cited by 92 publications

References 1 publication

Active Site Structure in Cytochrome c Peroxidase and Myoglobin Mutants: Effects of Altered Hydrogen Bonding to the Proximal Histidine

Active Site Structure in Cytochrome c Peroxidase and Myoglobin Mutants: Effects of Altered Hydrogen Bonding to the Proximal Histidine

Resonance Raman spectroscopy of oxoiron(IV) porphyrin π-cation radical and oxoiron(IV) hemes in peroxidase intermediates

Metastable intermediates in myoglobin at low pH.

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